Antenna device and communications device

ABSTRACT

A small antenna device having good communications performance and a wide communications area even when a metal plate is present in the antenna communications direction, even when the antenna is arranged, for example, inside a box-shaped metal case, and even when a through hole is used that has a smaller area than the antenna. This device comprises: the antenna ( 8 ); a rear surface cover ( 3 ) overlapping with the antenna ( 8 ) and being a conductor that faces the winding of the antenna ( 8 ); two first insulating areas ( 10   a ) provided in the rear surface cover ( 3 ) and extending in a direction that intersects the winding axis of the antenna ( 8 ); and a second insulating area ( 10   b ) that connects between the first insulating areas ( 10   a ). At least part of the area sandwiched by the first insulating areas ( 10   a ) faces the antenna ( 8 ).

TECHNICAL FIELD

The present invention relates to an antenna apparatus and acommunication apparatus that communicate with a wireless communicationmedium such as an IC card or IC tag of RF-ID or NFC, for example.

BACKGROUND ART

For conventional RF-ID (Radio Frequency Identification) or NFC (NearField Communication) antennas, how to deal with adjacent metal objectshas been a problem. That is, when these antennas are each accommodatedin a communication apparatus, the antenna is placed while beingsurrounded by a metal part such as a metal case, electromagnetic waveshield, metal plate inside a liquid crystal panel, or a frame forsecuring strength. Therefore, when an antenna performs communication, aneddy current that weakens the current or magnetic field of the antennaflows through the metal part, thus deteriorating the communicationperformance of the antennas. The communication performance deterioratessignificantly particularly when a metal body is placed in thecommunication direction of the antenna.

Thus, an antenna apparatus is proposed which will improve thecommunication characteristics of a loop antenna using a peripheral metalplate (e.g., see PTL 1). That is, a metal plate is provided with athrough hole (opening) and a slit, and the through hole and the openingof the loop antenna are arranged to overlap with each other so that thedirection of the current flowing through the loop antenna matches thedirection of the eddy current flowing through the outer circumference ofthe metal plate. In other words, the outer circumference of the metalplate is used as an antenna.

CITATION LIST Patent Literature PTL 1

-   Japanese Patent Publication No. 4684832

SUMMARY OF INVENTION Technical Problem

However, since the technique described in PTL 1 uses a loop antenna, itis difficult to reduce the size of the antenna to a certain degree ormore. That is, it is difficult to maintain the communicationcharacteristics of the loop antenna without securing the area of theopening, so that the shape of the antenna tends to extendtwo-dimensionally and it is thus difficult to downsize the antenna andto improve the communication characteristics at the same time. Moreover,the through hole formed in the metal plate has substantially the samesize as the opening of the loop antenna, so that it is necessary to forma large through hole in the metal plate or the like, causing a reductionin the strength of the metal plate or to reduce the size of the openingof the loop antenna, causing deterioration of the communicationcharacteristics. In addition, since the outer circumference of the metalplate is used as an antenna, the desired performance cannot be obtainedwhen a box-shaped metal case is used.

An object of the present invention is to provide an antenna apparatusand a communication apparatus provided with a wider communicable regionthan a loop antenna, with a downsized antenna even when the antenna isplaced inside a box-shaped metal case, or with a through hole having asmaller area than the antenna.

Solution to Problem

An antenna apparatus according to an aspect of the present inventionincludes: a coil antenna including a wound coil; a conductor thatincludes a surface facing the wound coil of the coil antenna and that isplaced so that a winding axis of the coil antenna is parallel to ordiagonally crosses the surface; at least two first insulating regionsprovided in the conductor and placed apart from each other in a windingaxis direction of the coil antenna; and a second insulating region thatconnects between the at least two first insulating regions, in which alongitudinal direction of each of the at least two first insulatingregions crosses the winding axis direction of the coil antenna, and atleast part of a region between two outermost ones of the at least twofirst insulating regions on the surface of the conductor faces the coilantenna.

Advantageous Effects of Invention

According to the present invention, it is possible to achieve goodcommunication performance with a downsized antenna even when the antennais placed inside a box-shaped metal case, or with a through hole havinga smaller area than the antenna. Furthermore, it is possible to providean antenna apparatus and a communication apparatus including a widercommunicable region than a loop antenna.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is an exploded perspective view of a portable terminal in whichan antenna according to an embodiment of the present invention isinstalled;

FIG. 1B is an exploded perspective view of a portable terminal in whichan antenna according to the embodiment of the present invention isinstalled;

FIG. 2 is a perspective view of the antenna according to the embodimentof the present invention;

FIG. 3 is an exploded perspective view of the antenna according to theembodiment of the present invention;

FIGS. 4A and 4B illustrate a conductor placement section and anadjustment pattern of the antenna according to the embodiment of thepresent invention;

FIG. 5 is an exploded perspective view of a portable terminal in whichthe antenna according to the embodiment of the present invention isinstalled at a position different from that in FIG. 1;

FIGS. 6A to 6D illustrate inductance adjustment of the antenna accordingto the embodiment of the present invention;

FIG. 7 illustrates an example of manufacturing steps of the antennaaccording to the embodiment of the present invention;

FIGS. 8A and 8B illustrate a positional relationship between the antennaand a metal body according to the embodiment of the present invention;

FIGS. 9A and 9B illustrate a relationship between a current and magneticflux when the current flows through the antenna according to theembodiment of the present invention;

FIGS. 10A and 10B illustrate an eddy current that flows through themetal body when the current in FIG. 9 flows;

FIG. 11 illustrates a magnetic field generated by a current flowingthrough the metal body;

FIGS. 12A to 12H illustrate slits of the metal body according to theembodiment of the present invention;

FIG. 13 is a perspective view on rear cover side of the portableterminal according to the embodiment of the present invention;

FIG. 14 is a perspective view illustrating a positional relationshipbetween the antenna, first slits and a second slit according to theembodiment of the present invention;

FIG. 15A illustrates magnetic flux generated by the antenna in FIG. 14;

FIG. 15B illustrates magnetic flux generated by the antenna in FIG. 14;and

FIG. 16 illustrates an eddy current flowing through the rear cover bythe magnetic flux in FIG. 15.

DESCRIPTION OF EMBODIMENT

Hereinafter, an embodiment of the present invention will be described indetail with reference to the accompanying drawings.

An antenna apparatus according to an embodiment of the present inventionincludes: a coil antenna including a wound coil; a conductor thatincludes a surface facing the wound coil of the coil antenna and that isplaced so that a winding axis of the coil antenna is parallel to ordiagonally crosses the surface; at least two first insulating regionsprovided in the conductor and placed apart from each other in a windingaxis direction of the coil antenna; and a second insulating region thatconnects between the at least two first insulating regions, in which alongitudinal direction of each of the at least two first insulatingregions crosses the winding axis direction of the coil antenna, and atleast part of a region between two outermost ones of the at least twofirst insulating regions on the surface of the conductor faces the coilantenna. Thus, the antenna apparatus according to the present embodimentcan obtain good communication performance with a downsized antenna evenwhen the antenna is placed inside a box-shaped metal case, or with athrough hole having a smaller area than the antenna. Furthermore, it ispossible to provide an antenna apparatus and a communication apparatusincluding a wider communicable region than a loop antenna.

Embodiment

FIGS. 1A and 1B are exploded perspective views of a portable terminalmounted with an antenna according to an embodiment of the presentinvention. FIG. 1A shows a U-shaped slit and FIG. 1B shows an L-shapedslit. Portable terminal 1 is constructed of display panel 2 and rearcover 3, and battery 4, camera 5 and electronic circuit substrate 6accommodated between display panel 2 and rear cover 3, or the like. Asshown in FIG. 1, display panel 2 may be of a touch panel type with nooperation buttons or may not be of a touch panel type and may beprovided with operation buttons separately. Display panel 2 is a liquidcrystal panel and is provided with panel cover 2 a. Antenna 8, which isa coil antenna according to an embodiment of the present invention, ismounted on metallic rear cover 3 by attachment using an adhesive tape orfixing using a screw or the like. In the present embodiment, antenna 8is fixed to rear cover 3, but antenna 8 may also be fixed to a frame.The frame may be made of metal or resin. Antenna 8 is used to carry outcommunication, using a metal body (conductor) such as rear cover 3placed in a communication direction seen from antenna 8. The conductoris preferably a metal body, but may also be made of other materials. Forexample, when antenna 8 is to be used for communication beyond a metalbody placed closer to display panel 2 than antenna 8, a slit may beformed in the metal body to enable communication, and it does not matterwhether rear cover 3 is metal or not in that case. In the presentembodiment, antenna 8 is placed close to an upper edge portion of rearcover 3 (edge close to camera 5 which is far from battery 4) and placedbetween camera 5 and the upper edge portion of rear cover 3. First slit10 a and second slit 10 b are placed between a through hole for thecamera and the upper edge portion of rear cover 3 as is the case withantenna 8. Antenna 8 may be placed so as to overlap with battery 4, butplacing antenna 8 so as to overlap with thinner electronic circuitsubstrate 6 can reduce the thickness of whole portable terminal 1. Inthe present embodiment, rear cover 3 has a relatively flat shape, butrear cover 3 may also have a curved surface.

External connection terminals 8 a and 8 b for making connection toelectronic circuit substrate 6 to thereby form an antenna apparatus areprovided on the surface of antenna 8 which faces electronic circuitsubstrate 6. The connection between electronic circuit substrate 6 andantenna 8 may be made by pin contact, connector connection, soldering ofa conductor or the like. In the present embodiment, electronic circuitsubstrate 6 is provided with antenna input and output pins 7 a and 7 b.As is generally known, antenna input and output pins 7 a and 7 b areconnected to antenna control section 9 on electronic circuit substrate 6on which a matching circuit and a control IC or the like are placed. Theantenna apparatus is formed by connecting antenna input and output pins7 a and 7 b to a coil portion having end portions at external connectionterminals 8 a and 8 b provided on antenna 8. In addition to an RF-ID ICand matching circuit, components including a multifrequency antenna,speaker and RF module, for example, are placed in a space formed betweenrear cover 3 and display panel 2.

In FIG. 1A, rear cover 3 a is provided with a U-shaped slit. This slitis provided with two first slits 10 a substantially parallel to awinding axis of antenna 8 (coil axis, a conductor of antenna 8 is woundaround the coil axis) and second slit 10 b that connects between twofirst slits 10 a. Since first slits 10 a and second slit 10 b may becurved lines or bent lines, first slits 10 a and second slit 10 b mayform various shapes such as U-shape, H-shape, Z-shape, S-shape ornumbers like 2 and 5. In FIG. 1B, rear cover 3 is provided with anL-shaped slit. That is, the slit is made up of one first slit 10 a andone second slit 10 b. However, as is apparent from FIG. 1B, an edgeportion (edge) of rear cover 3 is used as second first slit 10 a. Themetal body such as rear cover 3 may be provided with a through hole, endportion, chip or the like corresponding to at least two first slits 10 aand one second slit 10 b.

Antenna 8 is placed near first slits 10 a and second slit 10 b. That is,the entire or most of antenna 8 may face or contact, or may be apartfrom rear cover 3 (metal body).

FIG. 2 is a perspective view of the antenna according to the embodimentof the present invention. FIG. 3 is an exploded perspective view of theantenna according to the embodiment of the present invention. FIGS. 4Aand 4B illustrate a conductor placement section of the antenna accordingto the embodiment of the present invention and a coil pattern and anadjustment pattern provided to the conductor placement section.

As shown in FIG. 2, antenna 8 of the present embodiment is provided withcore 11 formed of a magnetic body such as ferrite, amorphous, siliconsteel, permalloy, soft magnetic material, and flexible substrate 12arranged so as to wrap around core 11, in which a coil pattern(conductor) or the like is formed on a support mainly made of resin.According to the present embodiment, core 11 is made of ferrite and hasa size of 13.7×33.5×0.3 mm, which may be approximately 13.4 to 14mm×33.2 to 33.8 mm×0.27 to 0.33 mm due to dimensional variations inbaking. Core 11 is parallelepiped or rectangular parallelepiped plateshaped in particular. The term “coil pattern” used herein refers to onethat is used for generating magnetic lines of force for carrying outcommunication with a wireless communication medium such as IC card or ICtag (not shown). In FIG. 2 and FIG. 3, a coil pattern whose coil axis(winding axis of coil) is indicated by arrowed straight line S isformed. The coil pattern and an adjustment pattern which will bedescribed later are normally formed of a copper foil which is formedbetween two resin layers: a polyimide film and a cover lay or resistincluded in, for example, flexible substrate 12. A coil pattern is woundaround this coil axis S as a substantial center, and coil axis S issubstantially perpendicular to the coil pattern of flexible substrate12. A conductor pattern including this coil pattern formed on flexiblesubstrate 12 will be described later in detail with reference to FIG. 4.Note that the conductor is not limited to one based on a conductorpattern alone, but may also be formed by winding a metal wire or thelike around core 11 or forming a conductor film on core 11.

Core 11 has a shape extending two-dimensionally in an X direction and Ydirection as shown in FIG. 2 and is thin in a thickness directionperpendicular to the X direction (coil winding direction of antenna 8)and Y direction (the same direction as coil axis S (winding axis)). Thecoil pattern is wound along the X direction. Core 11 is preferablylongest in the X direction parallel to the coil pattern and thethickness in the thickness direction is preferably smaller than thewidths in the X direction and Y direction.

Flexible substrate 12 is actually divided into two portions holding core11 in between as shown in FIG. 3. Of flexible substrate 12 divided intotwo portions, one of the portions having external connection terminals 8a and 8 b is designated as lower flexible substrate 12 a and the otherwith no external connection terminals 8 a and 8 b is designated as upperflexible substrate 12 b, for convenience in the present embodiment. Aswill be described in detail later, lower flexible substrate 12 a andupper flexible substrate 12 b are bonded by solder. These substrates areconnected on two sides of flexible substrate 12 substantially parallelto coil axis S in the present embodiment. The terms “lower” and “upper”are assigned for convenience to facilitate understanding in FIG. 3 andthe upper side and lower side may be inverted when antenna 8 isinstalled on a device.

In the present embodiment, the width of upper flexible substrate 12 b inthe coil axis S direction is set so that core 11 does not stick out.Particularly when core 11 is made of fragile ferrite, this setting isintended to prevent fragments or residues of the ferrite from scatteringinside a communication apparatus into which antenna 8 is incorporated(e.g., portable terminal 1 in FIG. 1) causing an adverse influence onthe communication apparatus.

In the present embodiment, a double-sided adhesive tape is used as anadhesive layer to fix core 11 between lower flexible substrate 12 a andupper flexible substrate 12 b. That is, the double-sided adhesive tapeis attached between core 11 and lower flexible substrate 12 a andbetween core 11 and upper flexible substrate 12 b.

At least one of surfaces of core 11 respectively facing lower flexiblesubstrate 12 a and upper flexible substrate 12 b in the presentembodiment is provided with slits (not shown) at a pitch of, forexample, 2 to 5 mm beforehand. Since core 11 is divided into smallfragments using these slits, core 11 is provided with flexibility. Asdescribed above, the double-sided adhesive tape is attached to thesurface of core 11 of the present embodiment facing lower flexiblesubstrate 12 a or upper flexible substrate 12 b. Moreover, lowerflexible substrate 12 a and upper flexible substrate 12 b are providedwith flexibility from the beginning.

Thus, even when the location of rear cover 3 of portable terminal 1shown in FIG. 1 to which antenna 8 is attached has a curved surface,antenna 8 can be attached and placed along the curved surface. As aresult, at least part of core 11 may be divided through theaforementioned slits and formed of a plurality of small fragments. Ifcore 11 is used alone, core 11 would fall to pieces at this point intime. It is the double-sided adhesive tape attached to the surfacefacing lower flexible substrate 12 a or upper flexible substrate 12 b ofcore 11 that prevents core 11 from falling to pieces. Alternatively, anadditional protective tape may be provided. The above-describedconfiguration can prevent some of small fragments of core 11 divided bythe aforementioned slits in FIG. 2 and FIG. 3 from falling off andprevent the fallen small fragments or residues from scattering inside acommunication apparatus into which antenna 8 is incorporated (e.g.,portable terminal 1 in FIG. 1). As a result, it is possible to preventany adverse influence on the communication apparatus.

The method for fixing core 11 to flexible substrate 12 need not alwaysbe attachment using a double-sided adhesive tape to both sides of core11 as shown in the present embodiment. For example, only one of thesides of the above-described double-sided adhesive tape may be used forfixing. Instead of attaching the double-sided adhesive tape between core11 and each flexible substrate, lower flexible substrate 12 a and upperflexible substrate 12 b may be bonded together at two sides of flexiblesubstrate 12 which are substantially orthogonal to coil axis S and notbonded by solder. In this case, lower flexible substrate 12 a and upperflexible substrate 12 b need to be extended outward beyond the outeredge of core 11 in the coil axis S direction. This part may be bonded bydirectly applying an adhesive thereto other than the attachment usingthe double-sided adhesive tape as described above.

In the present embodiment, the double-sided adhesive tape is alsoattached to the surface of lower flexible substrate 12 a not facing core11, and this is intended to attach and fix antenna 8 to rear cover 3 ofportable terminal 1 in FIG. 1 above.

Using FIG. 3 again, the present embodiment will be described. Asdescribed above, in lower flexible substrate 12 a and upper flexiblesubstrate 12 b constituting flexible substrate 12, conductors are bondedtogether by solder at the two sides of flexible substrate 12substantially parallel to coil axis S. In FIG. 3, lower flexiblesubstrate 12 a is provided with adjustment pattern 13 which will beillustrated later in FIG. 4 and provided with pattern exposing portions17 a and 17 b for enabling bonding by soldering. Similarly, upperflexible substrate 12 b is also provided with pattern exposing portions19 a and 19 b to allow lower flexible substrate 12 a and upper flexiblesubstrate 12 b to be bonded together by soldering where a coil patternis divided into a plurality of portions and both ends of the dividedpattern are exposed, which will be illustrated later in FIG. 4.

In the present embodiment, solder plating is further applied beforehandto copper foils at both ends of the divided pattern exposed throughpattern exposing portions 19 a and 19 b of upper flexible substrate 12 bbefore flexible substrate 12 is incorporated. Moreover, gold plating isapplied beforehand to copper foils at both ends of the divided patternexposed through pattern exposing portions 17 a and 17 b provided onlower flexible substrate 12 a and copper foils of external connectionterminals 8 a and 8 b. This gold plating is indispensable for securingreliability and preventing corrosion when external connection terminals8 a and 8 b come into contact with antenna input and output pins 7 a and7 b provided on electronic circuit substrate 6. Thus, even when goldplating or solder plating is applied to a certain portion, the presentembodiment uses the expression that the copper foil of the portion is“exposed.” As a result, a single coil pattern is formed. The coilpattern formed on flexible substrate 12 and other conductor patterns areformed as shown in FIGS. 4A and 4B to be more specific.

FIG. 4A is identical to the perspective view of the antenna according tothe embodiment of the present invention shown in FIG. 2 and illustratesthe configuration of the upper flexible substrate. FIG. 4B is aperspective view of the lower flexible substrate of the antennaaccording to the embodiment of the present invention. In addition towinding pattern 14 a, lower flexible substrate 12 a includes externalconnection terminals 8 a and 8 b, and adjustment pattern 13.

Antenna 8 includes core 11 which is a magnetic body, winding patterns 14a and 14 b which are coil winding sections where a conductor is woundaround core 11, and adjustment pattern 13 which is an adjustment sectionconnected to one end of winding patterns 14 a and 14 b. Since adjustmentpattern 13 is formed at an end of core 11, adjustment pattern 13 is notinserted, for example, into winding pattern 14 a, and externalconnection terminal 8 a is connected to adjustment pattern 13 whileexternal connection terminal 8 b is connected to winding patterns 14 aand 14 b. Adjustment pattern 13 includes an adjustment pattern which isa plurality of adjustment conductors resulting from division into aplurality of portions in a longitudinal direction. The plurality ofadjustment conductors are connected together at both ends, and connectedat adjustment pattern end 13 a and external connection terminal 8 a inFIG. 4B.

That is, a plurality of winding patterns 14 a which become parts of thecoil pattern for carrying out communication with a wirelesscommunication medium such as an IC card or IC tag are formed on lowerflexible substrate 12 a parallel to each other and so as to cross coilaxis S. The plurality of winding patterns 14 b which become parts of thecoil pattern are formed on upper flexible substrate 12 b parallel toeach other and so as to cross coil axis S. The copper foils at both endsof the plurality of winding patterns 14 a and 14 b are respectively“exposed” through pattern exposing portions 17 a and 17 b and patternexposing portions 19 a and 19 b. In FIGS. 4A and 4B, winding patterns 14a and 14 b are formed in region B. It is adjustment pattern 13 which ispart of the coil pattern that is formed in region A of lower flexiblesubstrate 12 a. In the present embodiment, adjustment pattern 13 isformed only on lower flexible substrate 12 a and need not be formed onupper flexible substrate 12 b.

FIG. 5 is an exploded perspective view of a portable terminal in whichthe antenna according to the present embodiment is installed at aposition different from that in FIG. 1. Even when the antenna is placedon the center side of the communication apparatus as shown in FIG. 5,sufficient communication is possible, and the position where antenna 8is placed is not limited, and there is a high degree of freedom ofdesign. However, in the position where antenna 8 is placed in FIG. 1, astrong magnetic field is emitted in the distal end direction of portableterminal 1 and the antenna is more likely to react to an externalmagnetic field from the distal end direction, and can thereby easilycommunicate with a communicating party located in the distal enddirection of portable terminal 1.

FIGS. 6A to 6D illustrate inductance adjustment of the antenna accordingto the embodiment of the present invention. FIG. 6A illustrates a statewith no trimming on the adjustment pattern, FIG. 6B illustrates a statewith trimming performed at a first trimming point of the adjustmentpattern, FIG. 6C illustrates a state with trimming performed at a secondtrimming point of the adjustment pattern, and FIG. 6D is an enlargedview of the adjustment pattern.

When antenna 8 is connected to electronic circuit substrate 6 on whichantenna control section 9 including a matching circuit and others inFIG. 1 to become an antenna apparatus, the inductance of antenna 8becomes a factor for determining a resonance frequency of the antennaapparatus. The inductance of antenna 8 having the structure of thepresent embodiment is greatly affected by variations in the size of core11 shown in FIG. 2 to FIG. 4. This is easily understandable because theinfluences of the length and the ferrite shape equivalent to thecross-sectional area appear substantially in proportion to each other asdefined in the formula of self-inductance of solenoid(self-inductance=magnetic permeability×square of the number of turns perunit length×solenoid length×cross-sectional area).

Thus, since the inductance of antenna 8 varies, the resonance frequencyof the antenna apparatus in which antenna 8 is installed also varies.Wireless communication can be performed with a high probability andquality by adjusting this resonance frequency to be within apredetermined range from a central frequency defined in thecommunication standard (e.g., 13.56 MHz for RF-ID). By reducingvariations in the inductance at antenna 8 alone (e.g., reducing it towithin ±2%), it is possible to reduce variations in the resonancefrequency of the antenna apparatus in which antenna 8 is installed.Therefore, according to the present embodiment, it is possible to reducevariations in the inductance of antenna 8 caused by variations in thesize of core 11 of antenna 8 using adjustment pattern 13.

Antenna 8 of the present embodiment includes adjustment pattern 13 ofregion A and winding patterns 14 a and 14 b of region B shown in FIG.4A. In adjustment pattern 13, one pattern (conductor) is divided intothree adjustment conductors 13 b, 13 c and 13 d along a longitudinaldirection of adjustment pattern 13. Of course, the conductor may bedivided into two portions or four or more portions, and the number ofportions may be adjusted according to the size of antenna 8 and thedegree of variations. Irrespective of the number of portions, adjustmentconductor 13 b which is the innermost side of adjustment pattern 13preferably has substantially the same conductor width as windingpatterns 14 a and 14 b, and the wire width of adjustment conductor 13 cother than adjustment conductor 13 b or the like may be smaller thanthat of adjustment conductor 13 b. Reducing the wire width can achievedownsizing. The width of adjustment conductor 13 b on the innermost sideof adjustment pattern 13 is set to substantially the same as theconductor width of winding patterns 14 a and 14 b because there may be acase where, of adjustment pattern 13, only adjustment conductor 13 b mayremain through trimming as shown in FIG. 6C when the inductance value isadjusted, which will be described later.

Adjustment conductors 13 b to 13 d extend parallel to winding patterns14 a and 14 b. The term “trimming” used herein means disconnecting(insulating) the wire of the pattern through punching or laserprocessing at first trimming point 15 a, second trimming point 15 b orthe like. Note that most of winding patterns 14 a and 14 b andadjustment conductors 13 b to 13 d are basically placed so as to face(overlap with) core 11. This is natural for efficiently obtaining theantenna performance because core 11 has the function of collecting themagnetic flux.

Next, the method for adjusting an inductance value will be described. Inthe present embodiment, since adjustment pattern 13 is divided intothree adjustment conductors 13 b to 13 d, there are two trimming points:first trimming point 15 a and second trimming point 15 b. That is, whenadjustment pattern 13 is divided into n portions, (n−1) trimming pointsare formed, and the inductance value is adjusted by trimming or nottrimming one of these trimming points.

The distance from adjustment conductors 13 b to 13 d that can be handledas a single conductor by being connected at adjustment pattern end 13 aand external connection terminal 8 a to end portion 11 a of core 11differs in FIG. 6A to FIG. 6C. Adjustment conductors 13 b to 13 d aresubstantially parallel to end portion 11 a of core 11 and may bearranged while inclining to each other up to +45 degrees, but are notarranged to be at least perpendicular to each other.

In FIG. 6A, none of three adjustment conductors 13 b to 13 d is trimmed.Therefore, adjustment pattern 13 functions as a single thick conductorplaced near end portion 11 a of core 11 and adjustment conductor 13 dbecomes the outermost coil pattern. The distance from outermostadjustment conductor 13 d to end portion 11 a of core 11 is short.

In FIG. 6B, adjustment pattern 13 is trimmed (insulated) at firsttrimming point 15 a. Therefore, of adjustment pattern 13, it is onlyadjustment conductors 13 b and 13 c that are actually functioning. As aresult, adjustment conductor 13 c becomes the outermost coil pattern andthe distance from outermost adjustment conductor 13 c to end portion 11a of core 11 is large compared to FIG. 6A.

In FIG. 6C, adjustment pattern 13 is trimmed at second trimming point 15b. Therefore, it is only adjustment conductor 13 b that is actuallyfunctioning in adjustment pattern 13. As a result, adjustment conductor13 b becomes the outermost coil pattern and the distance from outermostadjustment conductor 13 b to end portion 11 a of core 11 is largecompared to FIGS. 6A and 6B.

In the antenna coil having the structure of the present embodimentconfigured by winding a coil around the core, both end portions of thecore where no coil is wound become an input and output port of magneticflux of the antenna, and therefore if the number of turns in the antennacoil is the same, the greater the sizes of the input and output port ofmagnetic flux, the greater the inductance value tends to become. FIG. 6Ashows the state in which the size of the input and output port ofmagnetic flux is smallest while FIG. 6C shows the state in which thesize of the input and output port of magnetic flux is largest.

As a result, since the distances from adjustment conductors 13 b to 13 dto end portion 11 a of core 11 differ from each other, the size of theinput and output port of magnetic flux changes. As a result, theinductance value of antenna 8 can be adjusted.

In both FIG. 6B and FIG. 6C, it is only necessary to trim a singlelocation. That is, no matter how many portions into which adjustmentpattern 13 may be divided, both ends of a plurality of adjustmentconductors 13 b, 13 c, 13 d . . . , and so forth are connected on theadjustment pattern end portion 13 a side and on the external connectionterminal 8 a side and are arranged in parallel. Therefore, it may bepossible to set the number of adjustment conductors (from inside core11) to be left as adjustment pattern 13 and the number of adjustmentconductors (from outside core 11) to be disconnected so that the lengthof the coil pattern and the distance between end portion 11 a of core 11and adjustment pattern 13 becomes a desired distance, and thus to trimonly a single location therebetween. Thus, always placing the adjustmentconductor to be left as adjustment pattern 13 on the inner side of core11 and always placing the adjustment conductor to be disconnected at theouter side of core 11 makes it possible to limit trimming points to be asingle location and easily adjust the inductance value of antenna 8.

FIG. 7 illustrates an example of manufacturing steps of the antennaaccording to the embodiment of the present invention.

As has already been described, at least one of the surfaces of core 11facing lower flexible substrate 12 a or upper flexible substrate 12 bshown in FIG. 3 is provided with slits (not shown) at a pitch of severalmm beforehand. These slits are formed before a baking step when core 11is created. As a preliminary stage of this baking step, slits are formedin a size and to a depth that would not cause core 11 to be easilybroken at the slits even after the baking step. When core 11 is thin, itmay not be necessary to form any slits. Moreover, instead of slits,small dents may be formed in the surface of core 11 at intervals ofabout 1 mm.

A double-sided adhesive tape is attached to one of the surfaces of core11 subjected to such a baking step, the surface facing lower flexiblesubstrate 12 a or upper flexible substrate 12 b (step S1 in FIG. 7). Thedouble-sided adhesive tape is attached to both surfaces of core 11 inthe present embodiment.

As is well known, each side of the double-sided adhesive tape issupported by a support film for ease of handling. As a matter of course,in step S1 in FIG. 7, when the double-sided adhesive tape is attached toboth surfaces of core 11 shown in FIG. 3, these support films remain. Inthis state, one of the surfaces of core 11 to which the double-sidedadhesive tape is attached is pressed by, for example, a roller (step S2in FIG. 7).

Then, at least part of core 11 is divided by the slits such that core 11is made up of a plurality of fragments. However, core 11 would not fallto pieces because the double-sided adhesive tape is attached to bothsurfaces of core 11. Even when the area of rear cover 3 of portableterminal 1 shown in FIG. 1 to which antenna 8 is attached has a curvedsurface, such a state of core 11 allows core 11 to be placed along thecurved surface.

When antenna 8 is incorporated or installed in portable terminal 1 (seeFIG. 1) or the like, stress not expected by the operator may be appliedto core 11. In this case, some small fragments of core 11 divided by theslits may fall, but it is possible to prevent scattering of thefragments or residues that have fallen inside the communicationapparatus (e.g., portable terminal 1 in FIG. 1) into which antenna 8 isincorporated. It is thereby possible to avoid any adverse influence onthe communication apparatus.

During the pressing by the roller, the aforementioned support film ofthe double-sided adhesive tape shown in FIG. 3 can prevent thedouble-sided adhesive tape from being attached to the roller or theworkbench facing the roller.

The double-sided adhesive tape to be attached to the side of lowerflexible substrate 12 a on which core 11 is not placed is attached aftercompletion of the placement, alignment and solder bonding of upperflexible substrate 12 b to lower flexible substrate 12 a, which will bedescribed later. This is an idea for using a low-cost double-sidedadhesive tape material that is not resistant to heat applied duringsolder bonding to eliminate the need for use of an expensiveheat-resistant tape.

As described above, core 11 which has been made bendable to a certainextent is placed on lower flexible substrate 12 a (step S3 in FIG. 7).In this case, core 11 is placed on lower flexible substrate 12 a afterpeeling the support film of the double-sided adhesive tape attached tothe surface of core 11 facing lower flexible substrate 12 a. Thelocation at which core 11 is placed is inside the area shown by a dottedline in FIG. 4A.

After placing core 11 shown in FIG. 3 on lower flexible substrate 12 a,upper flexible substrate 12 b is then placed from above core 11. In thiscase, upper flexible substrate 12 b is also placed after peeling thesupport film of the double-sided adhesive tape attached to the surfaceof core 11 facing upper flexible substrate 12 b. Upper flexiblesubstrate 12 b is aligned such that core 11 is placed inside the areabounded by dotted line shown in FIG. 4B (step S4 in FIG. 7).

Several methods are available to align lower flexible substrate 12 a andupper flexible substrate 12 b between which core 11 is placed. Forexample, though not shown in the drawings of the present embodiment,holes or markers of alignment pins may be provided beforehand at outeredges of lower flexible substrate 12 a and upper flexible substrate 12 band alignment is performed using the holes or markers. After performingsolder bonding between lower flexible substrate 12 a and upper flexiblesubstrate 12 b to be described hereinafter, unnecessary holes or markersmay be removed. This facilitates alignment between pattern exposingportions 17 a and 19 a and between pattern exposing portions 17 b and 19b, and can more reliably assemble flexible substrate 12 on which a coilpattern for communicating with a wireless communication medium such asan IC card or IC tag is formed. When holes or markers cannot beprovided, it is also possible to use a method of aligning upper flexiblesubstrate 12 b with lower flexible substrate 12 a using an imagerecognition apparatus and robot or the like.

After performing such alignment, lower flexible substrate 12 a issolder-bonded to upper flexible substrate 12 b (step S5 in FIG. 7).Here, the positions of the copper foils at both ends of the dividedpattern exposed by pattern exposing portions 19 a and 19 b of upperflexible substrate 12 b match the positions of the copper foils at bothends of the divided pattern exposed by pattern exposing portions 17 aand 17 b of lower flexible substrate 12 a. That is, in FIG. 3, since thepositions of the respective copper foils match, a single coil pattern isformed by solder-bonding lower flexible substrate 12 a to upper flexiblesubstrate 12 b.

Solder-bonding is performed by heating the overlapping area betweenpattern exposing portions 17 a and 19 a and the overlapping area betweenpattern exposing portions 17 b and 19 b. As described above, solderplating is applied beforehand to the copper foils at both ends of thedivided pattern exposed by pattern exposing portions 19 a and 19 b ofupper flexible substrate 12 b. Gold plating is applied beforehand to thecopper foils at both ends of the divided pattern exposed by patternexposing portions 17 a and 17 b provided on lower flexible substrate 12a. Therefore, when the part is heated, the solder plated to the copperfoil of upper flexible substrate 12 b melts and lower flexible substrate12 a is bonded to the copper foil.

The double-sided adhesive tape is not resistant to heat, so that onlythe area where pattern exposing portions 17 a and 19 a overlap and thearea where pattern exposing portions 17 b and 19 b overlap is heated soas to prevent heat from being applied to the double-sided adhesive tape.This heating apparatus for solder-bonding may be removed from flexiblesubstrate 12 after the solder melts, the copper foil of upper flexiblesubstrate 12 b is bonded to the copper foil of lower flexible substrate12 a, and the solder is cooled and solidified. As such a heating methodthat requires local, speedy and fine temperature control, bonding usingpulse heat is suitable, for example.

However, soldering through solder plating applied to pattern exposingportions 19 a and 19 b of upper flexible substrate 12 b alone may not beenough for bonding of lower flexible substrate 12 a to upper flexiblesubstrate 12 b. In such a case, a solder cream layer may be formed onone of both end portions of the divided pattern of pattern exposingportions 17 a and 17 b of lower flexible substrate 12 a and both endportions of the divided pattern of upper flexible substrate 12 b.

Note that an ACF (anisotropic conductive film) may be used instead ofthe aforementioned solder bonding. That is, before step S4 in FIG. 7above, an ACF is attached to one of pattern exposing portions 17 a and17 b of lower flexible substrate 12 a and pattern exposing portions 19 aand 19 b of upper flexible substrate 12 b shown in FIG. 3. In this case,step S5 in FIG. 7 above, that is, the solder bonding step isunnecessary.

Lastly, the double-sided adhesive tape is attached to the side of lowerflexible substrate 12 a on which core 11 is not placed (step S6 in FIG.7). As described above, this is because the double-sided adhesive tapeis not resistant to heat applied during solder bonding. As is generallyknown, each side of a double-sided adhesive tape is supported by asupport film for ease of handling. As a matter of course, in step S6 inFIG. 7, when the double-sided adhesive tape is attached to lowerflexible substrate 12 a of antenna 8 shown in FIG. 3, the support filmremains. This support film is peeled off before antenna 8 completedthrough the above-described steps as shown, for example, in FIG. 1 isinstalled in portable terminal 1.

Using the above-described steps, antenna 8 shown in FIG. 2 can beassembled extremely simply and with high accuracy. As illustrated usingFIG. 3 and FIG. 7, since the configuration is employed so that thedouble-sided adhesive tape is attached beforehand to both planes of core11, core 11 is aligned with flexible substrate 12 and then soldered,even if alignment of the core fails, alignment can be done over againbefore soldering. It is thereby possible to reduce the assembly rejectrate of antenna 8 shown in FIG. 2.

Lastly, the relationship between the metal body, the through holeprovided in the metal body, and antenna 8, and excited magnetic flux,which are features of the present embodiment will be described. Althoughantenna 8 (core 11) has a substantially square shape in FIG. 8 and afterFIG. 8 for simplicity of description, there is no particular limitationto the shape.

FIGS. 8A and 8B illustrate a positional relationship between the antennaand a metal body according to the embodiment of the present invention.FIG. 8A is a top view, and FIG. 8B is a cross-sectional view taken alongline C-C of FIG. 8A. FIGS. 9A and 9B illustrate a relationship between acurrent and magnetic flux when the current flows through the antennaaccording to the embodiment of the present invention. FIG. 9A is a topview, and FIG. 9B is a cross-sectional view taken along line D-D of FIG.9A. FIGS. 10A and 10B illustrate an eddy current that flows through themetal body when the current in FIG. 9 flows, FIG. 10A illustrates thesurface facing the antenna seen from above and FIG. 10B is the back sideshown in FIG. 10A seen from above. FIG. 11 illustrates a magnetic fieldgenerated by a current flowing through the metal body. Note that theaforementioned adjustment pattern is not shown in FIGS. 8A and 8B andFIGS. 9A and 9B to describe the features of the present embodiment in aneasily understandable manner. That is, although a mechanism of adjustinginductance is not always necessary in realizing the features of thepresent embodiment which will be described hereinafter, provision ofthat mechanism will enable more accurate communication.

As shown in FIG. 8, the antenna apparatus according to the embodiment ofthe present invention is provided with antenna 8 as a coil antennaformed by winding a coil and a metal body that overlaps with antenna 8and faces the wound coil of antenna 8. In the present embodiment, themetal body is used as rear cover 3, and rear cover 3 needs only to be ametal body and preferably has a plate shape in particular. Since an eddycurrent flowing through the wound coil of antenna 8 needs to flow overthe surface of the metal body in one direction, the metal body isprovided with a surface facing the wound coil of antenna 8, and thewinding axis of antenna 8 is parallel to this surface or antenna 8diagonally crosses this surface. Even when the surface of the metal bodyis perpendicular to the winding axis (coil axis) of antenna 8, theloop-shaped wound coil of antenna 8 may face the surface of the metalbody, but this does not include a case where an eddy current of thewound coil of this loop-shaped coil flows over the surface of the metalbody. That is, the current that flows through the wound coil facing thesurface of the metal body is not loop-shaped but one-directional. Theone direction is a direction that crosses second slit 10 b. It ispreferable that the winding axis of antenna 8 be substantially parallelto the surface of the metal body. This allows the current to efficientlyflow through the metal body and allows the intensity of the magneticfield generated by the metal body to improve.

Next, the principles behind the generation of a magnetic field on theback side of rear cover 3 by antenna 8 and rear cover 3 (metal body)according to the embodiment of the present invention will be described.First, if no slit is provided to rear cover 3, a current that flows intoor magnetic flux generated in antenna 8 provided with a metal body suchas rear cover 3 around antenna 8 is canceled out by an eddy current inan opposite direction that flows into rear cover 3 or magnetic fluxgenerated by the eddy current. The eddy current generated in rear cover3 also weakens the magnetic field applied from outside to antenna 8,making it difficult for the magnetic field to reach antenna 8. As aresult, the presence of the metal body causes the communicable region ofantenna 8 to be significantly reduced and also causes the communicationcharacteristics to deteriorate, making it extremely difficult forantenna 8 to communicate beyond the metal body.

On the other hand, the antenna apparatus according to the embodiment ofthe present invention enables communication as follows. For example, asshown in FIGS. 9A and 9B, when a current flows through the wound coil ofantenna 8, a current (eddy current) in a reverse direction of the woundcoil facing rear cover 3 flows through antenna 8. That is, in FIG. 9B,since the current flows through antenna 8 clockwise, a current flowsthrough the wound coil of antenna 8 facing the rear cover from right toleft. An eddy current mainly from left toward right flows through aportion of rear cover 3 facing antenna 8 (the region mainly betweenfirst slits 10 a in FIG. 10A) so as to cancel out the current directedfrom right to left. This eddy current flowing from left to right rotatesso as to form a loop around first slit 10 aa and first slit 10 abrespectively as shown in FIG. 10A. Note that the direction of thecurrent flowing around upper first slit 10 aa in FIG. 10A iscounterclockwise and the direction of the current flowing around lowerfirst slit 10 ab is clockwise. That is, the current flows so as to forma loop in a reverse direction. When the currents that have rotatedaround first slits 10 a respectively flow up to second slit 10 b, thecurrents flow to the backside of rear cover 3 through second slit 10 b.The current that has flown to the backside of the rear cover flows asshown in FIG. 10B. That is, the direction of the current that flowsaround upper first slit 10 aa in FIG. 10B is clockwise, and thedirection of the current that flows around lower first slit 10 ab iscounterclockwise. In the region sandwiched by first slits 10 a, acurrent flows from right to left following the flow of the current loopand flows to the front side of rear cover 3 using second slit 10 b.

Thus, in the same first slit 10 aa, the loop of the current that flowsaround first slit 10 aa in FIG. 10A (side which is the front side andfaces the antenna) and the loop of the current that flows around firstslit 10 aa in FIG. 10B (backside and communication direction side) areopposite to each other. Similarly, in the same first slit 10 ab, theloop of the current that flows around first slit 10 ab in FIG. 10A andthe loop of the current that flows around first slit 10 ab in FIG. 10Bare opposite to each other. On either side, the direction of the loop ofthe current that flows around first slit 10 aa is opposite to thedirection of the loop of the current that flows around first slit 10 ab.It is thereby possible to generate a magnetic field directed from firstslit 10 aa to first slit 10 ab or a magnetic field directed from firstslit 10 ab to first slit 10 aa.

As a result, the magnetic field generated by antenna 8 in the directiontoward rear cover 3 is canceled out by the current that flows throughrear cover 3 on the surface on the antenna 8 side (front side). However,since the magnetic field generated by antenna 8 in the direction towardrear cover 3 and the magnetic field generated by the current that flowsthrough rear cover 3 are in the same direction, the magnetic fieldgenerated by antenna 8 on the rear cover 3 side as shown in FIG. 11operates as if the magnetic field penetrates rear cover 3 and performscommunication.

The direction of the current flowing through the metal is notnecessarily limited to the above-described direction, and the currentflows along complicated paths. However, since the current in theabove-described direction mainly flows as a whole, a large flow is seenin the above-described direction.

The same applies to a case where a magnetic field is received fromoutside. That is, when a current distribution as shown in FIG. 10B isgenerated on the back side of rear cover 10 b by the magnetic field fromoutside, a current distribution as shown in FIG. 10A is generated on thefront side of rear cover 3, and the relationship in current between rearcover 3 and antenna 8 is as shown in FIGS. 9A and 9B. Antenna 8 canreceive the magnetic field and can be driven as if there were no rearcover 3 which is the metal body.

In order to operate in the manner described above, the following firstslit and the second slit are preferable. That is, first slit 10 a andsecond slit 10 b are arranged in and around a region where antenna 8 andthe metal body overlap with other. This region is, for example, a regionsandwiched by two first slits 10 a, a region sandwiched by each one offirst slits 10 a and second slit 10 b and their peripheries.

Basically, two first slits 10 a are formed. This is because two firstslits 10 a respectively become the entrance and exit of a magnetic fieldthat spreads on the back side of rear cover 3 (communication directionside and also the outside of the communication apparatus). Therefore, itis possible to use an external end portion of rear cover 3 which is themetal body or use another through hole such as a through hole for thecamera in FIG. 1. As is seen in FIG. 8A, when a vector is consideredwhich has a direction in which a point of intersection between each oneof first slits 10 a and second slit 10 b is assumed to be a start pointand the end opposite to the start point is assumed to be an end point,the vector is provided with a component in the same direction as that ofthe wound coil on the metal side (X direction in FIG. 2). That is, firstslit 10 a need not always be substantially parallel to the wound coil ofantenna 8 or substantially perpendicular to the winding direction ofantenna 8, and may also be diagonal thereto, in which case, however,first slit 10 a is at least not perpendicular to the winding axis ofantenna 8 or parallel to the winding axis of antenna 8 (first slit 10 adoes not extend parallel to the Y direction in FIG. 2).

Since first slit 10 a has a linear shape, a current flowing through rearcover 3 can rotate around first slit 10 a efficiently. As a result, themagnetic field formed is intensified and can thereby improve itscommunication characteristics.

The longitudinal direction of first slit 10 a is preferably parallel tothe conductor facing rear cover 3, that is, perpendicular to the coilaxis. In this way, the current that flows into rear cover 3 flowsefficiently and rotates around each first slit 10 a in a loop shape.First slit 10 a is preferably outside the wound coil portion of antenna8 when seen from above as shown in FIG. 8A. That is, first slit 10 adoes not face (does not overlap with) the wound coil portion of antenna8. It is thereby possible to mostly make the directions of the currentsthat flow outside first slits 10 a (opposite to the sides of first slits10 a facing each other) the same. Furthermore, core 11 of antenna 8preferably overlaps with first slits 10 a. In this way, the magneticfield that passes through slit 10 a of rear cover 3 is intensified bycore 11. When the magnetic field is intensified, the communicationcharacteristics and communicable distance improve.

The length of first slit 10 a in the longitudinal direction ispreferably longer than the width of antenna 8 in the same direction. Theopening area of first slit 10 a directly affects the opening area of themagnetic field generated in rear cover 3, when first slit 10 a is formedto be longer, the magnetic field is more intensified and thecommunication characteristics improve. When first slit 10 a is extendedto approximately twice the width of antenna 8 in the same direction, itis possible to improve both of the strength of rear cover 3 and thestrength of the magnetic field, which is desirable. As a matter ofcourse, first slit 10 a may be extended even more.

The width of first slit 10 a in a short direction is about 1 to 3 mm,and the greater the width, the greater the opening area can become. Thewidth of first slit 10 aa is appropriately 1 to 10 mm, for example, andfirst slit 10 aa and first slit 10 ab are preferably identical in width.When first slit 10 aa and first slit 10 ab are identical in width, it ispossible to form a magnetic field in a well-balanced manner, but theymay be different in width.

It is preferable that the distance from first slit 10 aa to antenna 8 besubstantially the same as the distance from first slit 10 ab to antenna8. It is preferable that first slit 10 aa and first slit 10 ab besubstantially identical in length. As a result, the loop of the currentflowing around first slit 10 aa becomes similar to the loop of thecurrent flowing around first slit 10 ab, which makes it possible to forma magnetic field in a well-balanced manner.

One second slit 10 b may be sufficient. A directional vector of secondslit 10 b whose start point and end point correspond to two points ofintersection with first slit 10 a has a component in the same directionas the winding axis (Y direction in FIG. 2). That is, the component isnot parallel to the winding coil direction (X direction). Second slit 10b is preferably parallel to the axial direction (Y direction) of antenna8. In this way, it is possible to connect between first slits 10 a inthe shortest distance and minimize the slit area. Minimizing the slitarea makes it possible to maintain the strength of rear cover 3. Secondslit 10 b is preferably outside antenna 8 when seen from above as shownin FIG. 8A. In this way, it is possible to maximize the area where firstslits 10 a overlap with antenna 8 and thereby improve thecharacteristics of antenna 8.

The width of second slit 10 b in a short direction is approximately 1 to3 mm, and the larger the better. As shown in FIG. 9B, the currentsflowing through the side walls of second slit 10 b are different indirection and may possibly cancel out each other. For this reason, thewidth of second slit 10 b in the short direction is preferably large,and setting the width of second slit 10 b to approximately 1 to 10 mmmake it possible to maintain both of the strength of rear cover 3 andthe strength of the magnetic field.

The width of second slit 10 b in the longitudinal direction ispreferably longer than the width of antenna 8 in the same direction. Itis thereby possible to secure space for more currents to flow betweenfirst slits 10 a. As a result, the magnetic field generated by thecurrent flowing through rear cover 3 is intensified and thecommunication characteristics improve. The width of second slit 10 b inthe longitudinal direction is appropriately about 0.5 to 2 times thewidth of antenna 8 in the same direction, but may be a width withinother ranges.

First slit 10 a and second slit 10 b in the short direction need not bethe same width throughout the whole longitudinal direction, and thiswidth may vary.

When the entire or most of antenna 8 comes close to rear cover 3 (metalbody), the function for an eddy current flowing through rear cover 3 toweaken the current or magnetic field of antenna 8 increases, so that themagnetic field generated by rear cover 3 and the communicationcharacteristics can be improved. Meanwhile, when the entire or most partof antenna 8 is separated from rear cover 3 (metal body), the functionfor an eddy current flowing through rear cover 3 to weaken the currentor magnetic field of antenna 8 decreases, so that the communicationcharacteristics of antenna 8 itself can be improved. In the presentembodiment, since antenna 8 is attached to rear cover 3, a gap(clearance) having a size of approximately several tens to severalhundreds of μm is generated, the gap being equivalent to the thicknessof the insulated adhesive tape.

Regarding the shape of first slits 10 a and second slit 10 b, the shapemay be specifically shown in FIG. 12. As a matter of course, othershapes may also be adopted as long the above-described conditions aresatisfied. FIG. 12 illustrates metal body slits according to theembodiment of the present invention.

FIG. 12A shows the most efficient shape provided on rear cover 3 shownin FIG. 1A, FIG. 5 or the like. That is, since two first slits 10 a aresubstantially identical in width and length and are parallel to eachother, the loops of the currents flowing around the respective slits aresubstantially identical in size, which generates a magnetic fieldefficiently. Moreover, since second slit 10 b connects between endportions on the same sides of first slits 10 a, since second slit doesnot interrupt the current flowing through the region where second slit10 b is sandwiched between first slits 10 a.

In FIG. 12B, as described in FIG. 1B, the end portion of rear cover 3 isused as one first slit 10 a. Therefore, only one first slit 10 a isformed.

As shown in FIG. 12C, second slit 10 b may connect between intermediatepoints (may not necessarily be centers) of first slits 10 a. Thus, sincesecond slit 10 b is placed in a well-balanced manner betweenintermediate points of first slits 10 a, it is possible to enhance thestrength of the rear cover. Note that second slit 10 b may be placed soas to connect the centers in the longitudinal direction of first slits10 a to secure the efficiency of the current that flows through rearcover 3, and the strength.

As shown in FIG. 12D, three or more first slits 10 a may be provided.Though this is not advantageous from the standpoint of performance, sucha configuration is possible from the standpoint of design.

As shown in FIG. 12E, first slits 10 a may be formed to have a shortlength. That is, the length of the first slit in the longitudinaldirection may be about 0.5 times the length of antenna 8 in the samedirection. In this way, it is possible to form small slits and securethe strength of rear cover 3.

As shown in FIG. 12F, two first slits 10 a need not have the same lengthin the longitudinal direction.

As shown in FIG. 12G, second slit 10 b need not be perpendicular tofirst slits 10 a. Compared to FIG. 12A or the like, this shape improvesthe strength of rear cover 3. That is, this shape reduces the maximumarea of the region where the strength of the region becomes unstablewhen surrounded by first slits 10 a and second slit 10 b.

As shown in FIG. 12H, first slit 10 a and second slit 10 b may curve orbend. That is, the line may be C-shaped or U-shaped, arc-shape,wave-shape, serrated or the like.

In this way, first slit 10 a and second slit 10 b may adopt a variety ofshapes but they are not aligned on a single line or connected in a loopshape.

Next, variations of the present embodiment will be described. FIG. 13 isa perspective view of the portable terminal on the rear cover sideaccording to the embodiment of the present invention. FIG. 14 is aperspective view illustrating a positional relationship between theantenna, and first slit and second slit according to the presentembodiment. FIGS. 15A and 15B illustrate magnetic flux generated by theantenna in FIG. 14. FIG. 16 illustrates an eddy current that flowsthrough the rear cover by the magnetic flux in FIG. 15.

As shown in FIG. 13, one of first slits 10 a is provided whilepenetrating a through hole for camera 5 of rear cover 3 and an endportion of the slit extends to an end portion of rear cover 3. The otherone of first slits 10 a is provided such that part of its end portion ofrear cover 3 is chipped inward. That is, a part of each of slits 10 acorresponds to the end portion of rear cover 3. The end portion of rearcover 3 between both slits 10 a serves the role of second slit 10 b.Therefore, the end portion of rear cover 3 which corresponds to theportion of second slit 10 b should not be covered with anotherconductor. At least an end portion of the surface of the case (rear sideof rear cover 3 at the end of the case) is preferably made of aninsulator such as resin. This can be equivalent to quite a large slitbeing formed from the end portion of rear cover 3. The areas of firstslits 10 a and second slit 10 b are areas of the insulating regionswhich may be filled with an insulating member such as resin. In FIG. 13,the through hole for camera 5 is part of one first slit 10 a, but thethrough hole need not always be part of one of the slits. However, sucha configuration is efficient because the through hole for camera 5 canserve for two purposes. Although the other one of first slits 10 a isformed on the side wall of rear cover 3, the side wall is notnecessarily formed in rear cover 3. Whatever the case, a part of firstslit 10 a is connected to the end portion of rear cover 3 as long as theend portion of rear cover 3 is used as second slit 10 b. At least twofirst slits 10 a may be provided.

As shown in FIG. 14, the longitudinal direction of both first slits 10 ais a direction that crosses the winding axis direction of antenna 8 andis not parallel. The direction is preferably substantiallyperpendicular, and the term “substantially perpendicular” used hereinrefers to a relationship of 80 degrees to 100 degrees when“perpendicular” means 90 degrees. The length of both first slits 10 a inthe longitudinal direction is preferably longer than the width ofantenna 8 in the same direction and the communication characteristicsare thereby improved. Although the shape of first slit 10 a is linear,the shape is not limited to be linear and may be other shapes includinga curved line. However, first slit 10 a is provided with a longer slitwidth in the longitudinal direction than the slit width in otherdirections.

In FIG. 14, one first slit 10 a on the camera 5 side is substantiallyparallel to and substantially overlaps with (the term “overlap” usedherein does not always mean “contacting”) the end side of core 11 ofantenna 8. First slits 10 a may overlap with the coil wound section ofantenna 8, but preferably does not overlap because the characteristicsof antenna 8 would improve in this way. Therefore, one first slit 10 amay preferably overlap with the non-coil wound section of core 11 or maynot overlap with antenna 8 as in the case of other first slit 10 a. Whenone first slit 10 a does not overlap with antenna 8, the distancebetween first slit 10 a and antenna 8 is preferably 15 mm or less.

It can be seen in FIG. 15A that the magnetic flux generated by antenna 8extends outward from one first slit 10 a on the camera 5 side. It can beseen in FIG. 15B that the magnetic flux extends from one first slit 10 aon the camera 5 side to other first slit 10 a. Providing first slits 10a and second slit 10 b in this way makes it apparent that communicationof antenna 8 is enabled even when rear cover 3 is a conductor. Thedirection of the magnetic flux may be opposite.

It can be seen in FIG. 16 that an eddy current of rear cover 3 flowsaround one first slit 10 a on the camera 5 side in a loop shape. It canbe also seen that an eddy current flows around other first slit 10 a inan approximately semicircular loop caused by the eddy current.

In FIG. 14 and FIG. 16, an eddy current flows in the same direction asthat of the wound coil of antenna 8 right above antenna 8 on the surfaceof rear cover 3. This indicates that the same thing has occurred as thephenomenon that has occurred based on the principle described in FIG. 9and FIG. 10.

Thus, even when an end portion of rear cover 3 is used as at least partof first slit 10 a and second slit 10 b and an insulating region on theouter side of rear cover 3 is used, it is possible to obtain effectssimilar to those obtained when first slit 10 a and second slit 10 b arenot connected to the end portion of rear cover 3.

Thus, the regions of first slit 10 a and second slit 10 b may beinsulated or at least part thereof may be an end portion (edge) of rearcover 3 (conductor such as metal).

As described above, the antenna apparatus of the present embodimentincludes: antenna 8 of a wound coil; rear cover 3 that includes asurface facing the wound coil of antenna 8, that is placed so that awinding axis of antenna 8 and the surface are parallel to each other orto diagonally cross; at least two first insulating regions (first slits10 a) provided on rear cover 3 and arranged apart from each other in awinding axis direction of antenna 8; and a second insulating region(second slit 10 b) that connects between first slits 10 a. Thelongitudinal directions of respective first slits 10 a cross the windingaxis direction of antenna 8. The term “cross” used herein does notrequire the longitudinal directions to actually cross the winding axisdirection, but means that at least the longitudinal directions of firstslits 10 a are not parallel to the winding axis direction of antenna 8.In addition, at least part of the region between two first slits 10 afaces antenna 8 on the surface of rear cover 3.

The disclosure of Japanese Patent Application No. 2012-195870, filed onSep. 6, 2012, including the specification, drawings and abstract isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

According to the present invention, even when a small-sized antenna isplaced inside a box-shaped metal case, good communication performancecan be obtained with a through hole having a smaller area than theantenna. Furthermore, since it is possible to provide an antennaapparatus and a communication apparatus having a wider communicableregion than a loop antenna, the present invention is useful as a varietyof communication devices such as a mobile phone. The present inventionis also applicable to systems for drug management, dangerous goodsmanagement, valuable goods management or the like except storage rack orshowcase, particularly enabling automatic merchandise management or bookmanagement.

REFERENCE SIGNS LIST

-   1 Portable terminal-   2 Display panel-   3 Rear cover-   4 Battery-   5 Camera-   6 Electronic circuit substrate-   7 a, 7 b Antenna input and output pin-   8 Antenna-   8 a, 8 b External connection terminal-   9 Antenna control section-   10 a First slit-   10 b Second slit-   11 Core-   12 Flexible substrate-   12 a Lower flexible substrate-   12 b Upper flexible substrate-   13 Adjustment pattern-   13 a Adjustment pattern end-   13 b, 13 c, 13 d Adjustment conductor-   14 a, 14 b Winding pattern-   17 a, 17 b, 19 a, 19 b Pattern exposing portion-   20 Frame

1. Antenna apparatus comprising: a coil antenna including a wound coil;a conductor that includes a surface facing the wound coil of the coilantenna and that is placed so that a winding axis of the coil antenna isparallel to or diagonally crosses the surface; at least two firstinsulating regions provided in the conductor and placed apart from eachother in a winding axis direction of the coil antenna; and a secondinsulating region that connects between the at least two firstinsulating regions, wherein a longitudinal direction of each of the atleast two first insulating regions crosses the winding axis direction ofthe coil antenna, and at least part of a region between two outermostones of the at least two first insulating regions on the surface of theconductor faces the coil antenna.
 2. The antenna apparatus according toclaim 1, wherein a shape in the longitudinal direction of each of the atleast two first insulating regions is linear.
 3. The antenna apparatusaccording to claim 2, wherein the longitudinal directions of the firstinsulating regions are substantially parallel to the wound coil of thecoil antenna on a side of the wound coil facing the conductor.
 4. Theantenna apparatus according to claim 1, wherein a distance between thetwo outermost first insulating regions in the winding axis direction ofthe coil antenna is greater than a width of the coil antenna in the samedirection.
 5. The antenna apparatus according to claim 1, wherein alength of the first insulating region in the longitudinal direction islonger than a width of the antenna coil in the same direction.
 6. Theantenna apparatus according to claim 1, wherein a longitudinal directionof the second insulating region is substantially parallel to the windingaxis direction of the coil antenna.
 7. The antenna apparatus accordingto claim 1, wherein a length of the second insulating region in alongitudinal direction of the second insulating region is longer than orequal to a width of the antenna coil in the same direction.
 8. Theantenna apparatus according to claim 1, wherein the second insulatingregion of the conductor does not face the coil antenna.
 9. The antennaapparatus according to claim 1, wherein the antenna coil is attached tothe conductor.
 10. The antenna apparatus according to claim 1, whereinthe antenna coil is placed apart from the conductor.
 11. The antennaapparatus according to claim 1, wherein the first insulating regions arefilled with an insulator.
 12. The antenna apparatus according to claim1, wherein the at least two first insulating regions are each connectedto an end portion of the conductor.
 13. A communication apparatuscomprising the antenna apparatus according to claim 1, wherein theconductor is at least part of a case that accommodates the antennaapparatus.